1. Field of Invention
The present invention addresses launch, retrieval, and servicing of a hovering aircraft, especially in turbulent winds or onto an irregularly-moving surface, such as the deck of a ship in a rough sea. Various embodiments of the present invention are especially suited to unmanned aircraft of small size. These embodiments allow for a fully automated operations cycle, whereby the aircraft can be repeatedly launched, retrieved, serviced, and re-launched, without manual intervention at any point, and while requiring only modest accuracy in piloting.
2. Description of Problem
Hovering aircraft, be they helicopters, thrust-vectoring jets, “tail-sitters”, or other types, usually land by gently descending in free thrust-borne flight onto a landing surface, coming to rest on an undercarriage of wheels, skids, or legs. This elementary technique can be problematic in certain situations, such as when targeting a small, windswept landing pad on a ship moving in a rough sea. Decades ago, the Beartrap or RAST system was developed to permit retrieval with acceptable safety in such conditions. Retrieval with this system involves securing a line between a helicopter and landing deck, and then winching the helicopter down onto a trolley. The helicopter is fastened to the trolley. After retrieval, the trolley is used to move the helicopter along the deck. The system is effective and widely used, but requires an expensive and substantial plant in the landing area, as well as manual operations coordinated between helicopter and shipboard crew. Furthermore, the helicopter must carry a complete undercarriage in addition to the necessary Beartrap components.
Desirable improvements relative to the Beartrap system include (a) simplification of the apparatus, and (b) automated rather than manual operation. Ideally not only would retrieval but also subsequent refueling and launch would be automated. This would be particularly desirable for an unmanned aircraft, whose operations cycle could then be made fully autonomous. Some experimental work toward this objective has been done for a hovering aircraft, as described in the publication by Mullens et al. titled, “Automated Launch, Recovery, and Refueling for Small Unmanned Aerial Vehicles” (2004); however, success has been limited even with light wind and a stationary base. The present invention by contrast provides for fully automated operation in calm or rough conditions, using apparatus which is simple, portable, and suitable for a small vessel or similarly confined base.